from datetime import timedelta

from django.db import IntegrityError, transaction
from django.db.models import Q, Sum
from django.shortcuts import get_object_or_404
from django.utils import timezone
from django.utils.crypto import get_random_string
from drf_spectacular.utils import extend_schema
from rest_framework.exceptions import NotFound, PermissionDenied
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

from .models import FamilyLink, ParentalSettings, WeeklyReportLog
from .serializers import (
    FamilyLinkAcceptRequestSerializer,
    FamilyLinkAcceptResponseSerializer,
    FamilyLinkInviteRequestSerializer,
    FamilyLinkInviteResponseSerializer,
    FamilyLinkStatusResponseSerializer,
    FamilySettingsResponseSerializer,
    FamilySettingsUpdateRequestSerializer,
    FamilySettingsUpdateResponseSerializer,
    FamilyWeeklyReportResponseSerializer,
)


def _week_start(dt):
    """دوشنبه‌ی هفته‌ی جاری (ISO weekday) برای dt داده‌شده."""
    return (dt - timedelta(days=dt.weekday())).date()


class FamilyLinkInviteView(APIView):
    """POST /api/family/link/invite — دعوت فرزند توسط والد (تولید کد اتصال)"""

    permission_classes = [IsAuthenticated]

    @extend_schema(
        request=FamilyLinkInviteRequestSerializer,
        responses=FamilyLinkInviteResponseSerializer,
        tags=['Family (family)'],
    )
    def post(self, request):
        serializer = FamilyLinkInviteRequestSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        v = serializer.validated_data

        # دعوت pending موجود برای همین شماره، به‌جای رکورد تکراری، برگردانده می‌شود.
        link = FamilyLink.objects.filter(
            parent_user_id=request.user.id, child_phone=v['childPhone'], status='pending'
        ).first()

        if not link:
            # اگر برخورد روی invite_code باشد (نه دعوت همین parent/child)، کد جدید
            # تولید و دوباره تلاش می‌شود؛ در غیر این صورت رکورد pending موجود برگردانده می‌شود.
            for attempt in range(5):
                code = get_random_string(6, allowed_chars='0123456789')
                try:
                    with transaction.atomic():
                        link = FamilyLink.objects.create(
                            parent_user_id=request.user.id,
                            child_phone=v['childPhone'],
                            invite_code=code,
                        )
                    break
                except IntegrityError:
                    link = FamilyLink.objects.filter(
                        parent_user_id=request.user.id, child_phone=v['childPhone'], status='pending'
                    ).first()
                    if link is not None:
                        break
                    # برخورد روی invite_code بوده؛ کد جدید ساخته و دوباره تلاش می‌شود.
                    continue
            else:
                raise IntegrityError(
                    'Could not generate a unique family invite code after several attempts.'
                )

        data = {'familyLinkId': str(link.pk), 'inviteCode': link.invite_code, 'status': link.status}
        return Response(FamilyLinkInviteResponseSerializer(data).data)


class FamilyLinkAcceptView(APIView):
    """POST /api/family/link/accept — تأیید دعوت توسط فرزند"""

    permission_classes = [IsAuthenticated]

    @extend_schema(
        request=FamilyLinkAcceptRequestSerializer,
        responses=FamilyLinkAcceptResponseSerializer,
        tags=['Family (family)'],
    )
    def post(self, request):
        serializer = FamilyLinkAcceptRequestSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        v = serializer.validated_data

        # ردیف FamilyLink زیر قفل خوانده می‌شود تا دو accept هم‌زمان روی همان
        # invite_code هر دو کامل نشوند و دو بار notify() ارسال نشود.
        with transaction.atomic():
            link = get_object_or_404(
                FamilyLink.objects.select_for_update(),
                invite_code=v['inviteCode'], status='pending',
            )

            # اگر دعوت برای شماره‌ی مشخصی صادر شده باشد، فقط همان شماره می‌تواند accept کند.
            if link.child_phone and link.child_phone != request.user.phone:
                raise PermissionDenied('این دعوت متعلق به شماره‌ی دیگری است.')

            # اتمیک: تغییر وضعیت لینک + ساخت Notification یک واحد است.
            link.child_user_id = request.user.id
            link.status = 'accepted'
            link.accepted_at = timezone.now()
            link.save(update_fields=['child_user_id', 'status', 'accepted_at'])

            # رویداد FamilyLinkAccepted — طبق سند معماری، Notifications فقط
            # event-listener‌ه؛ دقیقاً همون الگوی notify() که در
            # support/admin.py هنگام پاسخ تیکت صدا زده می‌شه.
            from notifications.services import notify

            notify(
                user_id=link.parent_user_id,
                type='family_link_accepted',
                title='فرزند شما دعوت را پذیرفت',
                related_id=link.id,
            )

        data = {'familyLinkId': str(link.pk), 'status': link.status, 'acceptedAt': link.accepted_at}
        return Response(FamilyLinkAcceptResponseSerializer(data).data)


class FamilyLinkStatusView(APIView):
    """GET /api/family/link — وضعیت اتصال والد-فرزند (برای هر دو طرف)"""

    permission_classes = [IsAuthenticated]

    @extend_schema(responses=FamilyLinkStatusResponseSerializer, tags=['Family (family)'])
    def get(self, request):
        link = FamilyLink.objects.filter(
            Q(parent_user_id=request.user.id) | Q(child_user_id=request.user.id)
        ).first()
        if not link:
            raise NotFound('اتصال خانوادگی پیدا نشد.')

        child_name = ''
        if link.child_user_id:
            from accounts.models import User as AccountUser

            child = AccountUser.objects.filter(id=link.child_user_id).first()
            child_name = child.name if child else ''

        data = {'familyLinkId': str(link.pk), 'status': link.status, 'childName': child_name}
        return Response(FamilyLinkStatusResponseSerializer(data).data)


class FamilySettingsView(APIView):
    """GET/PATCH /api/family/settings — تنظیمات کنترل والدین"""

    permission_classes = [IsAuthenticated]

    def _get_settings(self, request):
        link = get_object_or_404(FamilyLink, parent_user_id=request.user.id, status='accepted')
        settings_obj, _ = ParentalSettings.objects.get_or_create(family_link=link)
        return settings_obj

    @extend_schema(responses=FamilySettingsResponseSerializer, tags=['Family (family)'])
    def get(self, request):
        settings_obj = self._get_settings(request)
        data = {
            'dailyLimitMinutes': settings_obj.daily_limit_minutes,
            'quietHoursStart': settings_obj.quiet_hours_start,
            'quietHoursEnd': settings_obj.quiet_hours_end,
        }
        return Response(FamilySettingsResponseSerializer(data).data)

    @extend_schema(
        request=FamilySettingsUpdateRequestSerializer,
        responses=FamilySettingsUpdateResponseSerializer,
        tags=['Family (family)'],
    )
    def patch(self, request):
        settings_obj = self._get_settings(request)
        serializer = FamilySettingsUpdateRequestSerializer(data=request.data, partial=True)
        serializer.is_valid(raise_exception=True)
        v = serializer.validated_data

        update_fields = []
        if 'dailyLimitMinutes' in v:
            settings_obj.daily_limit_minutes = v['dailyLimitMinutes']
            update_fields.append('daily_limit_minutes')
        if 'quietHoursStart' in v:
            settings_obj.quiet_hours_start = v['quietHoursStart']
            update_fields.append('quiet_hours_start')
        if 'quietHoursEnd' in v:
            settings_obj.quiet_hours_end = v['quietHoursEnd']
            update_fields.append('quiet_hours_end')

        if update_fields:
            settings_obj.save(update_fields=update_fields)

        return Response(FamilySettingsUpdateResponseSerializer({'success': True}).data)


class FamilyWeeklyReportView(APIView):
    """
    GET /api/family/weekly-report — آخرین گزارش هفتگی

    طبق سند معماری، این گزارش خودش داده تکراری نگه نمی‌داره و از API
    اپ‌های Progress و Curriculum خونده می‌شه؛ چون این پروژه یک مونولیت
    جنگویی‌ه، همون «خوندن» با import مستقیم مدل‌های آن دو اپ پیاده‌سازی
    شده — دقیقاً همون الگویی که progress/views.py (LeaderboardView) برای
    خوندن نام کاربر از accounts.User استفاده می‌کنه.
    """

    permission_classes = [IsAuthenticated]

    @extend_schema(responses=FamilyWeeklyReportResponseSerializer, tags=['Family (family)'])
    def get(self, request):
        link = get_object_or_404(FamilyLink, parent_user_id=request.user.id, status='accepted')

        week_start = _week_start(timezone.now())
        with transaction.atomic():
            log, created = WeeklyReportLog.objects.get_or_create(
                family_link=link, week_start=week_start, defaults={'sent_at': timezone.now()}
            )

            if created:
                from notifications.services import notify

                notify(
                    user_id=link.parent_user_id,
                    type='weekly_report_ready',
                    title='گزارش هفتگی فرزند شما آماده است',
                    related_id=log.id,
                )

        from content.models import UserLessonCompletion
        from progress.models import StreakRecord

        completions = UserLessonCompletion.objects.filter(
            user_id=link.child_user_id, created_at__date__gte=week_start
        )
        xp_earned = completions.aggregate(total=Sum('xp_earned'))['total'] or 0
        lessons_completed = completions.count()

        streak = StreakRecord.objects.filter(user_id=link.child_user_id).first()
        current_streak = streak.current_streak if streak else 0

        if not log.opened_at:
            log.opened_at = timezone.now()
            log.save(update_fields=['opened_at'])

        data = {
            'weekStart': week_start,
            'xpEarned': xp_earned,
            'lessonsCompleted': lessons_completed,
            'currentStreak': current_streak,
            'openedAt': log.opened_at,
        }
        return Response(FamilyWeeklyReportResponseSerializer(data).data)